This invention relates to ruthenium carbonylates and processes for their preparation. More specifically, the invention relates to the ruthenium carbonylate anions [Ru.sub.4 (CO).sub.11 ].sup.6-, [Ru.sub.6 (CO).sub.17 ].sup.4-, and [Ru.sub.6 (CO).sub.16 ].sup.6- together with the salts and acids of these anions, and the processes for the preparation of all these compounds.
In U.S. Pat. No. 4,349,521 (which describes an invention of one of us (Sheldon G. Shore) and Colleen C. Nagel, and which is assigned to the same assignee as the present application) and in a paper by the said Sheldon G. Shore and Colleen C. Nagel in J. Chem. Soc. Chem. Comm., 1980, page 530, there are described processes for the preparation of various ruthenium carbonylate anions by the controlled reduction of triruthenium dodecacarbonyl, Ru.sub.3 (CO).sub.12. This controlled reduction of triruthenium dodecacarbonyl is effected by treatment with a mixture of an alkali metal, an electron carrier compound able to carry an electron produced by the ionization of the alkali metal to the triruthenium dodecacarbonyl and a solvent which will solubilize the electron-bearing form of the carrier compound. As will be apparent to those skilled in the art, the actual reducing agent in such processes is the electrons produced by ionization of the alkali metal to form alkali metal cations, the electrons thus produced being transferred to the triruthenium dodecacarbonyl by the electron carrier compound. The product of the reduction reaction varies with the molar ratio of alkali metal:triruthenium dodecacarbonyl employed; at a molar ratio of 1:1, the product is [Ru.sub.6 (CO).sub.18 ].sup.2-, at a molar ratio of about 1.5:1 the product is [Ru.sub.4 (CO).sub.13 ].sup.2-, at a molar ratio of 2:1 the product is [Ru.sub.3 (CO).sub.11 ].sup.2-, and at a molar ratio of 3:1 the product is [Ru.sub.4 (CO).sub.12 ].sup.4-.
We have now discovered that if the molar ratio of alkali metal to triruthenium dodecacarbonyl in the above reaction increased at least to about 4.5:1, a novel ruthenium carbonylate anion of the formula [Ru.sub.4 (CO).sub.11 ].sup.6- is formed; the formation of this anion is surprising because hitherto no ruthenium carbonylate anions bearing such a high charge have been known. We have also discovered that the same anion may be produced by reacting the anion [Ru.sub.4 (CO).sub.12 ].sup.4- produced as described above with the same mixture of alkali metal, carrier compounds and solvent provided at least about 2 moles of the alkali metal are used for each mole of [Ru.sub.4 (CO).sub.12 ].sup.4-. We have also discovered that anions [Ru.sub.6 (CO).sub.17 ].sup.4-, and [Ru.sub.6 (CO).sub.16 ].sup.6- which apparently cannot be produced directly by reduction of triruthenium dodecacarbonyl can be produced by treating [Ru.sub.6 CO.sub.18 ].sup.2- with an alkali metal, together with the electron carrier compound and solvent used in the aforementioned reactions. Finally, we have discovered that the anion [Ru.sub.6 (CO).sub.16 ].sup.6- can also be prepared by treating [Ru.sub.6 (CO).sub.17 ].sup.4- with an alkali metal, together with the electron carrier compound and solvent used in the aforementioned reactions.